Package org.eclipse.rdf4j.query.algebra.evaluation

Interface QueryEvaluationStep

All Known Subinterfaces:

SliceQueryEvaluationStep

All Known Implementing Classes:

BindingSetAssignmentQueryEvaluationStep, ExtensionQueryEvaluationStep, FedXZeroLengthPathEvaluationStep, IntersectionQueryEvaluationStep, JoinQueryEvaluationStep, LeftJoinQueryEvaluationStep, MinusQueryEvaluationStep, OrderQueryEvaluationStep, ProjectionQueryEvaluationStep, RdfStarQueryEvaluationStep, ReificationRdfStarQueryEvaluationStep, ServiceQueryEvaluationStep, SliceQueryEvaluationStep.OffSetAndLimitQueryEvaluationStep, SliceQueryEvaluationStep.OnlyLimitQueryEvaluationStep, SliceQueryEvaluationStep.OnlyOffsetQueryEvaluationStep, StatementPatternQueryEvaluationStep, UnionQueryEvaluationStep, ZeroLengthPathEvaluationStep

Functional Interface:

This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.

@FunctionalInterface
public interface QueryEvaluationStep

A Step that may need to be executed in a EvaluationStrategy. The evaluate method should do the minimal work required to evaluate given the bindings. As much as possible should be pre-computed (e.g. resolving constant values)

Nested Class Summary

Nested Classes

Modifier and Type	Interface	Description
static class	QueryEvaluationStep.DelayedEvaluationIteration	Utility class that removes code duplication and makes a precompiled QueryEvaluationStep available as an iteration that may be created and used later.

Field Summary

Fields

Modifier and Type	Field	Description
static final QueryEvaluationStep	EMPTY
static final EmptyIteration<BindingSet>	EMPTY_ITERATION

Method Summary

Modifier and Type	Method	Description
static QueryEvaluationStep	empty()
CloseableIteration<BindingSet>	evaluate(BindingSet bindings)
static QueryEvaluationStep	minimal(EvaluationStrategy strategy, TupleExpr expr)	A fall back implementation that wraps a pre-existing evaluate method on a strategy
static QueryEvaluationStep	wrap(QueryEvaluationStep qes, Function<CloseableIteration<BindingSet>,CloseableIteration<BindingSet>> wrap)	Wrap an QueryEvalationStep: where we apply a function on every evaluation result of the wrapped EvaluationStep.

Field Details

EMPTY_ITERATION

static final EmptyIteration<BindingSet> EMPTY_ITERATION

EMPTY

static final QueryEvaluationStep EMPTY

Method Details

evaluate

CloseableIteration<BindingSet> evaluate(BindingSet bindings)

minimal

static QueryEvaluationStep minimal(EvaluationStrategy strategy,
 TupleExpr expr)

A fall back implementation that wraps a pre-existing evaluate method on a strategy

Parameters:

strategy - that can evaluate the tuple expr.

expr - that is going to be evaluated

Returns:

a thin wrapper arround the evaluation call.

empty

static QueryEvaluationStep empty()

wrap

static QueryEvaluationStep wrap(QueryEvaluationStep qes,
 Function<CloseableIteration<BindingSet>,CloseableIteration<BindingSet>> wrap)

Wrap an QueryEvalationStep: where we apply a function on every evaluation result of the wrapped EvaluationStep. Useful to add a timing function

Parameters:

qes - an QueryEvaluationStep that needs to return modified evaluation results

wrap - the function that will do the modification

Returns:

a new evaluation step that executes wrap on the inner qes.